Rainwater tank

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Some of the rainwater tanks around CERES Community Environment Park, in Melbourne, Australia

A rainwater tank (sometimes called a rain barrel in North America in reference to smaller tanks, or a water butt in the UK) is a water tank used to collect and store rain water runoff, typically from rooftops via pipes. Rainwater tanks are devices for collecting and maintaining harvested rain. A rainwater catchment or collection (also known as "rainwater harvesting") system can yield 2,358 litres (623 US gal) of water from 2.54 cm (1.00 in) of rain on a 92.9 m2 (1,000 sq ft) roof.

Contents

Rainwater tanks are installed to make use of rain water for later use, reduce mains water use for economic or environmental reasons, and aid self-sufficiency. Stored water may be used for watering gardens, agriculture, flushing toilets, in washing machines, washing cars, and also for drinking, especially when other water supplies are unavailable, expensive, or of poor quality, and when adequate care is taken that the water is not contaminated and is adequately filtered.

Underground rainwater tanks can also be used for retention of stormwater for release at a later time and offer a variety of benefits. In arid climates, rain barrels are often used to store water during the rainy season for use during dryer periods.

Rainwater tanks may have a high (perceived) initial cost. However, many homes use small scale rain barrels to harvest minute quantities of water for landscaping/gardening applications rather than as a potable water surrogate. These small rain barrels, often recycled from food storage and transport barrels or, in some cases, whiskey and wine aging barrels, are often inexpensive. There are also many low cost designs that use locally available materials and village level technologies for applications in developing countries where there are limited alternatives for potable drinking water. [1] While most are properly engineered to screen out mosquitoes, the lack of proper filtering or closed loop systems may create breeding grounds for larvae. With tanks used for drinking water, the user runs a health risk if maintenance is not carried out. [2]

Contamination and maintenance

If rainwater is used for drinking, it is often filtered first. Filtration (such as reverse osmosis, ultraviolet sterilization, or ultrafiltration) may remove pathogens. While rain water is pure it may become contaminated by particulate matter in the air as it falls or during collection. [3] While rain water does not contain chlorine, contamination from airborne pollutants, which settle onto rooftops, may be a risk in urban or industrial areas. Many water suppliers and health authorities, such as the New South Wales Department of Health, do not advise using rainwater for drinking when there is an alternative mains water supply available. However, reports of illness associated with rainwater tanks are relatively infrequent, and public health studies in South Australia (the Australian state with the highest rainwater usage rate) have not identified a correlation. Rainwater is generally considered fit to drink if it smells, tastes and looks fine; [4] however, some pathogens, chemical contamination and sub-micrometre suspended metal may produce neither smell nor taste and may not be visible.[ citation needed ]

Australian standards may differ greatly from other places in the world where rainwater is commonly used for drinking water. In the United States, rainwater is being increasingly used throughout the country for various purposes. In the semi-arid western state of New Mexico, for instance, many residents in the Taos and Santa Fe areas in particular use rainwater either for landscaping purposes or even all household uses (including potable indoor water). The "smells, tastes, and looks fine" standard used in the above paragraph is not an absolute indicator of rainwater safety. Most people who are rainwater users for potable purposes in the US make certain that their water is safe through filtration, ultraviolet sterilization, and testing.

Certain paints and roofing materials may cause contamination. In particular, a Melbourne Water publication advises that lead-based paints never be used. Tar-based coatings are also not recommended, as they affect the taste of the water. Zinc can also be a source of contamination in some paints, as well as galvanized iron [5] or zincalume roofs, particularly when new, should not collect water for potable use. Roofs painted with acrylic paints may have detergents and other chemicals dissolve in the runoff. Runoff from fibrous cement roofs should be discarded for an entire winter, due to leaching of lime. Chemically treated timbers and lead flashing should not be used in roof catchments. Likewise, rainwater should not be collected from parts of the roof incorporating flues from wood burners without a high degree of filtration. Overflows or discharge pipes from roof-mounted appliances such as air conditioners or hot-water systems should not have their discharge feed into a rainwater tank.

"Copper Poisoning", a 2010 news article, linked copper poisoning to plastic tanks. The article indicated that rainwater was collected and stored in plastic tanks and that the tank did nothing to mitigate the low pH. [6] The water was then brought into homes by copper piping. The copper was released by the high acid rainwater and caused poisoning in humans. It is important to note that, while the plastic tank is an inert container, the collected acid rain could and should be analysed and pH adjusted before being brought into a domestic water supply system. The solution is to monitor stored rainwater with swimming pool strips, cheap and available at swimming pool supply outlets.

If the water is too acidic, the state, county or local health officials may be contacted to obtain advice, precise solutions and pH limits, and guidelines as to what should be used to treat rainwater to be used as domestic drinking water.

Maintenance includes checking roofs and rain gutters for vegetation and debris, maintaining screens around the tank, and occasionally desludging (removing sediment by draining and cleaning the tank of algae and other contaminants).

Rainwater tanks which are not properly sealed (secured at the top) may act as breeding grounds for mosquitoes. [7]

Several options for dealing with the mosquito issue are: 1. Flushing all water once a week 2. Using a small amount of cooking oil to suffocate the larvae (the water is still suitable for landscape use after this) 3. Adding the bacillus Bt to the water. This bacteria will not harm animals. 4. Adding mosquito-eating fish

Another way to store rainwater without worry of contamination by mosquitoes is to use underground storage tanks. Underground tanks keep the water too cool (12.8 °C (55.0 °F)) for mosquito larvae and also are dark, preventing both mosquito, bacterial, and algae growth. An article by Richard Hill goes into depth about the benefits of underground rainwater storage. [8]

Tanks

Example of caged IBC totes being used for rainwater harvesting Rain-IBC-Example.jpg
Example of caged IBC totes being used for rainwater harvesting

Rainwater tanks may be constructed from materials such as plastic (polyethylene), concrete, galvanized steel, as well as fiberglass and stainless steel which are rust and chemical-resistant. Full tanks are usually installed above ground, and are usually opaque to prevent the exposure of stored water to sunlight, to decrease algal bloom. [3]

Tanks may be covered and have screen inlets to exclude insects, debris, animals and bird droppings. Almost all steel tanks currently produced for household rainwater collection come with a plastic inner lining to increase the life of the tank, prevent leaks and protect the water quality.

Apart from rooftops, tanks may also be set up to collect rainwater from concrete patios, driveways and other impervious surfaces.

Initial sizes typically ranged in capacity from around 400 to 100,000 litres (110 to 26,420 US gal), today modern technology has allowed modular and scalable applications to go into sizes of millions of litres or hundreds of thousands of US gallons. [9]

Smaller tanks, such as the plastic (208 litres (55 US gal)-barrel) are also used in some cases. Larger tanks are commonly used where there is no access to a centralised water supply. Companies recommend a 1,135 litres (300 US gal) tank for a house supporting two people (if compost toilets are placed) and if the region receives at least 762 mm (30.0 in) of precipitation a year. If it receives less (between 254–762 mm (10.0–30.0 in), two or three of these 300-gallon tanks can be placed so that more rain can be gathered at times when it does rain. Also affecting tank size is predicted rainfall and rainfall variability; the higher prices for larger tanks; intended use of rainwater and typical consumption for these uses; the area of roof draining into the tank; security of supply desired.

Large polyethylene rainwater tanks being installed Rainwater tanks 01 pengo.jpg
Large polyethylene rainwater tanks being installed

Most rainwater catchment tanks used throughout the world are composed of virgin polyethylene, a substance which in the US is both FDA and NSF approved for potable water storage. Other types of tanks used for rainwater storage include fiberglass, galvanized metal, stainless steel, and concrete. Each type of tank has positive and negative aspects. Polyethylene tanks, when placed above ground, can be subject to algae growth as well as the possibility of a short life (about 20 years) due to normal UV exposure in sunlight. The very strong fiberglass tanks must undergo a specific coating process to be brought up to potable grade. Galvanized tanks must either be lined or coated both for potability as well as to prevent the inevitable rusting at any welded seams. Uncoated galvanized tanks will leach zinc into the stored water and are not recommended in most instances - certainly not for water stored for human consumption. Concrete tanks leach a more benign substance, lime, into stored water and many are used around the world for rainwater storage.

One method of harvesting rain water has been is modular, scalable systems which are installable underground. These came as an evolution of a geosynthetic applications called Infiltration Tanks, which when stacked provide a void space volume which allows for the storing of water. Improved and more cost effective industrial design now allow for theoretically limitless storage of water underground.

Water supply augmentation

In Australia, the brand TransTank International manufactures portable water tanks from specially formulated polyethylene for transport and static applications. In some cities, installation of rainwater tanks may be mandatory, or may help a new building be approved. For example, in Victoria, Australia, new houses which have rainwater tank connected to all flush toilets are given an additional 1-star of the required 5-star House Energy Rating. Some governments subsidise purchases of rainwater tanks or provide rebates in areas where they are considered an important means of water supply augmentation. [10] In the United States, Santa Fe County, New Mexico requires a rainwater collection system on all new construction with greater than 2,500 square feet, mostly for landscaping purposes and to prevent over-reliance on wells but in some instances because ground water is prohibitively expensive to obtain, if even available.

Rainwater to supplement drinking water supplies may be seen as an alternative to other water supply options such as recycling or seawater desalination. Tanks are often perceived to have environmental costs that are comparatively lower than other water supply augmentation options.

Rainwater collection can be made compatible with centralised water supply by tapping it using an electropump.

Widespread use of rain barrels also changes the amount of rainwater reaching the ground in a particular area and draining into streams. Depending on the climate, this either helps prevent erosion, sedimentation, and/or pollution, and can reduce the strain on stormwater drainage systems; or it could cause rivers to dry up and ponds to stagnate if the water is diverted to a different watershed. If collected water is used in the same watershed in which it is collected, rainwater collection actually can stabilize flow in rivers and provide more regular and filtered groundwater transfer into ponds.

Colorado law

In the State of Colorado, United States, the installation of rainwater collection barrels is subject to the Constitution of the State of Colorado, state statutes and case law. [11] This is a consequence of the system of water rights in the state; the movement and holding of rainwater is inextricably linked with ownership of water rights and is enshrined in the constitution of the State of Colorado. The use of water in Colorado and other western states is governed by what is known as the prior appropriation doctrine. This system of water allocation controls who uses how much water, the types of uses allowed, and when those waters can be used. This is often referred to as the priority system or "first in time, first in right." Since all water arriving in Colorado has been allocated to "senior water right holders" since the 1850s, rainwater prevented from running downstream may not be available to its rightful owner. In 2009, legislation in Colorado was enacted that permits capture of rain water for residential use subject to strong limitations and conditions. [12] To be permitted, a residence may not be connected to a domestic water supply system serving more than three single-family dwellings. The permit must be purchased from the State Engineer's office and is subject to water usage restrictions. [13]

Internal rainwater tank

Rainwater tanks or drums may be used inside a house to provide thermal mass for a trombe wall (or water wall). Rainwater Hog modular tanks invented by Sally Dominguez to fit within building structure were used in the Modabode House of the Future floor and on the foyer wall of the Department of Sustainability building in Anglesea, Victoria, harnessing the higher value of the stored rainwater to add effective thermal mass to the enclosed spaces. [14]

Specially designed rainwater tanks can also be embedded in or under the concrete slab of a building (stab tank).

A house in Cape Schanck, Victoria, Australia, uses an internal rainwater tank to provide cooling to the living room in summer. During winter the tank is drained and wrapped in an insulating jacket. The tank also provides structural support to the roof, and excess water is used for domestic use including drinking. [15] [16]

See also

Related Research Articles

<span class="mw-page-title-main">Plumbing</span> Systems for conveying fluids

Plumbing is any system that conveys fluids for a wide range of applications. Plumbing uses pipes, valves, plumbing fixtures, tanks, and other apparatuses to convey fluids. Heating and cooling (HVAC), waste removal, and potable water delivery are among the most common uses for plumbing, but it is not limited to these applications. The word derives from the Latin for lead, plumbum, as the first effective pipes used in the Roman era were lead pipes.

<span class="mw-page-title-main">Tap water</span> Publicly available water supplied to homes

Tap water is water supplied through a tap, a water dispenser valve. In many countries, tap water usually has the quality of drinking water. Tap water is commonly used for drinking, cooking, washing, and toilet flushing. Indoor tap water is distributed through indoor plumbing, which has existed since antiquity but was available to very few people until the second half of the 19th century when it began to spread in popularity in what are now developed countries. Tap water became common in many regions during the 20th century, and is now lacking mainly among people in poverty, especially in developing countries.

<span class="mw-page-title-main">Storm drain</span> Infrastructure for draining excess rain and ground water from impervious surfaces

A storm drain, storm sewer, surface water drain/sewer, or stormwater drain is infrastructure designed to drain excess rain and ground water from impervious surfaces such as paved streets, car parks, parking lots, footpaths, sidewalks, and roofs. Storm drains vary in design from small residential dry wells to large municipal systems.

<span class="mw-page-title-main">Barrel</span> Hollow cylindrical container

A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden staves and bound by wooden or metal hoops. The word vat is often used for large containers for liquids, usually alcoholic beverages; a small barrel or cask is known as a keg.

<span class="mw-page-title-main">Rainwater harvesting</span> Accumulation of rainwater for reuse

Rainwater harvesting (RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a tank, cistern, deep pit, aquifer, or a reservoir with percolation, so that it seeps down and restores the ground water. Dew and fog can also be collected with nets or other tools. Rainwater harvesting differs from stormwater harvesting as the runoff is typically collected from roofs and other surfaces for storage and subsequent reuse. Its uses include watering gardens, livestock, irrigation, domestic use with proper treatment, and domestic heating. The harvested water can also be committed to longer-term storage or groundwater recharge.

<span class="mw-page-title-main">Cistern</span> Waterproof receptacle for holding liquids, usually water

A cistern is a waterproof receptacle for holding liquids, usually water. Cisterns are often built to catch and store rainwater. Cisterns are distinguished from wells by their waterproof linings. Modern cisterns range in capacity from a few litres to thousands of cubic metres, effectively forming covered reservoirs.

<span class="mw-page-title-main">Intermediate bulk container</span> Industrial-grade storage and transport container for fluids and solids

Intermediate bulk containers are industrial-grade containers engineered for the mass handling, transport, and storage of liquids, semi-solids, pastes, or solids. The two main categories of IBC tanks are flexible IBCs and rigid IBCs. Many IBCs are reused or repurposed.

<span class="mw-page-title-main">Bunding</span> Retaining wall around pollution source

Bunding, also called a bund wall, is a constructed retaining wall around storage "where potentially polluting substances are handled, processed or stored, for the purposes of containing any unintended escape of material from that area until such time as a remedial action can be taken."

<span class="mw-page-title-main">Water tank</span> Container for storing water

A water tank is a container for storing water. They are used to provide storage of water for use in many applications, drinking water, irrigation agriculture, fire suppression, agricultural farming, both for plants and livestock, chemical manufacturing, food preparation as well as many other uses. Water tank parameters include the general design of the tank, and choice of construction materials, linings. Various materials are used for making a water tank: plastics, fiberglass, concrete, stone, steel. Earthen pots, such as matki used in South Asia, can also be used for water storage. Water tanks are an efficient way to help developing countries to store clean water.

<span class="mw-page-title-main">Rain gutter</span> Component of a water discharge system

A rain gutter, eavestrough, eaves-shoot or surface water collection channel is a component of a water discharge system for a building. It is necessary to prevent water dripping or flowing off roofs in an uncontrolled manner for several reasons: to prevent it damaging the walls, drenching persons standing below or entering the building, and to direct the water to a suitable disposal site where it will not damage the foundations of the building. In the case of a flat roof, removal of water is essential to prevent water ingress and to prevent a build-up of excessive weight.

<span class="mw-page-title-main">Potable water diving</span> Underwater diving in potable water systems

Potable water diving is diving inside a tank that is used for potable water. This is usually done for inspection and cleaning tasks. A person who is trained to do this work may be described as a potable water diver. The risks to the diver associated with potable water diving are related to the access, confined spaces and outlets for the water. The risk of contamination of the water is managed by isolating the diver in a clean dry-suit and helmet or full-face mask which are decontaminated before the dive.

<span class="mw-page-title-main">Flexible tank</span> Storage container

Flexible tanks are a kind of storage equipment for liquids such as water or oil. Compared to steel tanks, flexible tanks have many advantages, including lighter weight and being rustproof, foldable, and quicker and easier to set up. With the same capacity, an empty flexible tank may have just 10% of a steel tank's weight. The disadvantages of flexible tanks include lower durability and shorter longevity. Some flexible tanks can be used as transport containers on trucks, ships, or aeroplanes, with some suitable for use in airdrops, helicopter swing, or hauling water.

<span class="mw-page-title-main">Stormwater harvesting</span>

Stormwater harvesting or Stormwater reuse is the collection, accumulation, treatment or purification, and storage of stormwater for its eventual reuse. While rainwater harvesting collects precipitation primarily from rooftops, stormwater harvesting deals with collection of runoff from creeks, gullies, ephemeral streams, underground conveyances. It can also include catchment areas from developed surfaces, such as roads or parking lots, or other urban environments such as parks, gardens and playing fields.

<span class="mw-page-title-main">Water-sensitive urban design</span> Integrated approach to urban water cycle

Water-sensitive urban design (WSUD) is a land planning and engineering design approach which integrates the urban water cycle, including stormwater, groundwater, and wastewater management and water supply, into urban design to minimise environmental degradation and improve aesthetic and recreational appeal. WSUD is a term used in the Middle East and Australia and is similar to low-impact development (LID), a term used in the United States; and Sustainable Drainage System (SuDS), a term used in the United Kingdom.

<span class="mw-page-title-main">Water storage</span> Storage of water by various means

Water storage is a broad term referring to storage of both potable water for consumption, and non potable water for use in agriculture. In both developing countries and some developed countries found in tropical climates, there is a need to store potable drinking water during the dry season. In agriculture water storage, water is stored for later use in natural water sources, such as groundwater aquifers, soil water, natural wetlands, and small artificial ponds, tanks and reservoirs behind major dams. Storing water invites a host of potential issues regardless of that water's intended purpose, including contamination through organic and inorganic means.

Rainwater harvesting in the United Kingdom is a practice of growing importance. Rainwater harvesting in the UK is both a traditional and reviving technique for collecting water for domestic uses and is generally used for non-hygienic purposes like watering gardens, flushing toilets, and washing clothes. In commercial premises like supermarkets it is used for things like toilet flushing where larger tank systems can be used collecting between 1000 and 7500 litres of water. It is claimed that in the South East of England there is less water available per person than in many Mediterranean countries.

<span class="mw-page-title-main">Water supply and sanitation in Gibraltar</span>

Water supply and sanitation in Gibraltar have been major concerns for its inhabitants throughout its history, from medieval times to the present day. The climate of Gibraltar is a mild Mediterranean one with warm dry summers and cool wet winters. Since daily records of rainfall began in 1790, annual rainfall has averaged a mean of 838 millimetres (33.0 in) with the highest volumes in December and the lowest in July. However, most of Gibraltar's small land area is occupied by the Rock of Gibraltar, a limestone outcrop that is riddled with caves and crevices. There are no rivers, streams, or large bodies of water on the peninsula, which is connected to Spain via a narrow sandy isthmus.

<span class="mw-page-title-main">Rainwater harvesting in Canada</span>

Rainwater harvesting is becoming a procedure that many Canadians are incorporating into their daily lives, although data does not give exact figures for implementation. Rainwater can be used for a number of purposes including stormwater reduction, irrigation, laundry and portable toilets. In addition to low costs, rainwater harvesting is useful for landscape irrigation. Many Canadians have started implementing rainwater harvesting systems for use in stormwater reduction, irrigation, laundry, and lavatory plumbing. Provincial and municipal legislation is in place for regulating the rights and uses for captured rainwater. Substantial reform to Canadian law since the mid-2000s has increased the use of this technology in agricultural, industrial, and residential use, but ambiguity remains amongst legislation in many provinces. Bylaws and local municipal codes often regulate rainwater harvesting.

<span class="mw-page-title-main">Caged IBC tote</span> Bulk container design type

Caged IBC totes are one of, if not the most commonly used, of all current intermediate bulk container design types. Caged IBC totes are handling and shipping containers for the storing, transit, and operation integration of various commodities, with the most common being water. Caged IBCs are often utilized as one-use containers, especially when it comes to hazardous materials, but are also suitable for reuse under many conditions. This IBC type often features an interior liner, blow-mold manufactured from polyethylene, that is structurally supported by a protective cage frame, often of galvanized steel composition. Caged IBCs are engineered for the bulk handling of liquids, semi-solids, as well as solid materials. All materials can present certain safety and compatibility concerns, especially hazardous liquids, and proper guidance is always recommended whenever using caged IBC totes for harsh chemicals.

<span class="mw-page-title-main">Water canister</span>

A water container, water canister or water can is a medium-sized portable container for transport, storage and use of water. Large plastic bottles are sometimes called "canisters". Water canisters can for example be used for drinking water, wastewater or showering. Water canisters are used for excursions, camping, boat trips, in cabins without tap water, or as a household drinking water reserve in case of emergency.

References

  1. Camilli, Luis (2000), Rainwater Harvesting: constructing a cistern and gutter system using village technologies and materials, Maji Safi Rainwater Harvesting Manual
  2. "Rainwater, Fact Sheet". greenhouse.gov.au: Your Home Technical Manual. Archived from the original on 2007-02-16. Retrieved 2007-02-17.
  3. 1 2 Texas Water Development Board; Chris Brown Consulting; Jan Gerston Consulting; Stephen Colley/Architecture; Hari J. Krishna (2005). The Texas Manual on Rainwater Harvesting (PDF). Texas Water Development Board. p. 88 pages. Archived from the original (PDF) on 2009-01-06.
  4. "Buying guide: Rainwater tanks". CHOICE magazine. Retrieved 2007-02-10.
  5. M.I. Magyar; V.G. Mitchell; A.R. Ladson; C. Diaper (2008). "Lead and other heavy metals: common contaminants of rainwater tanks in Melbourne" (PDF). Water Down Under 2008. CSIRO: 415. "Aluminium and cadmium can be an impurity in zinc galvanised iron roofs (Gromaire et al., 2001, Van Metre and Mahler, 2003) and therefore found in collected tank rainwater. Indeed, in Study 2, the tank with high concentration of Cd collected water from a galvanised iron roof."
  6. "Copper poisoning linked to plastic water tanks". ABC South East NSW. Retrieved 2010-11-28.
  7. The Sunday Age. November 25, 2007. "These flies! Will mozzies be next?". Stephen Cauchi quoting Luke Simpkin, Museum Victoria.
  8. http://www.whitewaterlimited.com/BacterialActivityinHarvestedRainWater.pdf [ bare URL PDF ]
  9. "Water management for life" (PDF). Archived from the original (PDF) on 2011-02-26. Retrieved 2010-02-07.
  10. "Energy efficiency for Victoria, action plan" (PDF). Archived from the original (PDF) on 2007-08-31. Retrieved 2007-05-22.
  11. "Water harvesting in Colorado" (PDF). Archived from the original (PDF) on 2007-08-16. Retrieved 2007-08-30.
  12. Colorado Division of Water Resources (2009-07-01). "New information on rainwater collection legislation" (PDF). Archived from the original (PDF) on 2012-04-29. Retrieved 2009-07-13.
  13. Colorado General Assembly (2009-07-01). "Colorado Senate Bill 09-080" (PDF). Retrieved 2009-11-07.
  14. "Thecoolhunter.net - ECO HOME". Archived from the original on 2008-10-13. Retrieved 2008-09-17.
  15. "materialicio.us is registered with pair Domains". materialicio.us. Retrieved 5 April 2018.
  16. "architecture.com.au - The Royal Australian Institute of Architects (RAIA), architecture, architects, design, australia". globalconstruct.net. Archived from the original on 3 June 2016. Retrieved 5 April 2018.

Further reading

  • Rainwater Tanks (PDF), NSW Health
  • WSUD Engineering Procedures: Stormwater. Robin Allison, Matt Francey. 2005 (Melbourne Water). CSIRO Publishing.
  • Eaton, Andrew D.; Greenberg, Arnold E.; Rice, Eugene W.; Clesceri, Lenore S.; Franson, Mary Ann H., eds. (2005). Standard Methods For the Examination of Water and Wastewater (21 ed.). American Public Health Association. ISBN   978-0-87553-047-5. Also available on CD-ROM and online by subscription.